1. Field of the Invention
The present invention generally relates to a spread-spectrum generator, and more particularly, to a spread-spectrum generator which can tune the delay time.
2. Description of Related Art
In an electronic circuit, a spread-spectrum generator apparatus is usually used to disperse the frequency of the signal, to prevent the energy of the signal from concentrating on a certain frequency. Frequency of a clock signal which is not performed with a spread-spectrum operation is constant. Energy of such clock signal is concentrated at a signal spectrum tone, and an electromagnetic interference (EMI) thereof is relatively severe. For most electronic devices or packages, electromagnetic interference (EMI) is a common but undesirable disturbance that may interrupt, obstruct, degrade or limit the effective performance of the devices or the whole circuit.
In order to prevent electromagnetic interference (EMI) caused by harmonic of single frequency, spread-spectrum skill is applied. Spread-spectrum means modulating the frequency of a clock signal so that the energy of the clock signal is distributed into more spectrum tones in order to reduce electromagnetic interference of the clock signal. Therefore, such spread-spectrum skill is one of the most popular approaches for solving the EMI problem.